July 7, 2011 at 8:53 a.m.

Cole crop pests are unique

Cole crop pests are unique
Cole crop pests are unique

I must admit that before I was a Master Gardener, I didn't realize what vegetables were regarded as cole crops. They include cabbage, cauliflower, Brussels sprouts, broccoli, kale, kohlrabi, and turnips.

A real advantage of cole crops is they can be put in the garden early in the spring, even when the soil is cool. Cole crops are also some of the last vegetables to leave the garden in the fall. An example is Brussels sprouts that should not be harvested until after a hard frost because they sweeten' even after the ground is frozen solid.

This long growth period gives insects a long time to feed on the cole crop family.

Cabbage loopers, cabbage worms, and diamond-back moths are the most common caterpillar pests in cole crops. Of the three, imported cabbage worms are the most frequent and usually cause the most damage in home gardens. They are velvety green with faint yellow strips running lengthwise down the back and sides. Full grown caterpillars are one-inch long. Their feeding on outer leaves of cabbage does little real damage, but caterpillars inside cabbage or broccoli heads can be very destructive. In early summer, many are carried away by yellow jackets and paper wasps, but those embedded in the plants can be a real problem.

The cabbage loopers are pale green with white lines down each side. Since the loopers have no legs in the middle section they have a characteristic looping motion when they move across vegetation. Full grown they are about one to one inche long. Differing from the cabbage worm adults, looper adults are nocturnal moths, but can be seen resting on the underside of host plants during the day. The moths are dark brown with small, white squiggles in the middle of their wings.

Diamondback moths are also nocturnal. The moths are light brown and slender. When the moths are at rest their folded wings show a pattern of three diamonds. They are much smaller than either cabbage worms or cabbage loopers. Mature diamondbacks are about one-third inch long, light green, tapered at both ends, and wiggle vigorously when touched.

Cole crops, like many vegetables, can tolerate some feeding damage. Extensive feeding can also prevent the head formation of cabbage, cauliflower, and broccoli. If you decide to use insecticides, the best time to treat the caterpillars is when they are still small, Bacillius thuringiensis (BT) is less toxic and will not harm beneficial insects. More aggressive spraying with pesticides such as permethin (eight) or carbaryl (seven) will kill beneficial insects such as bees so be careful and go by the directions on the label.

Note: In a previous article about the end of the Spring Harvest, it was mentioned that you should pull the old rhubarb out. Some people thought that meant to pull every stalk that has been unused. What I meant was that you should pull some of the old stalks laying on the ground, starting to turn brown.


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